[vsnet-chat 2849] (fwd) TASS Variable Carbon Stars (Greaves)

[Taichi Kato <tkato>]

(fwd) TASS Variable Carbon Stars (Greaves)

Date: Sat, 22 Apr 2000 11:40:13 +0000
From: JG <jgts@jgws.totalserve.co.uk>
Subject: TASS Variable Carbon Stars

The following TASS variables [data gleaned from Taichi Kato's newvar.cat
list] are listed as Carbon Stars in the CGCS = 'Cool Galactic Carbon
Stars, 2nd Edition (Stephenson C.B., Publ. Warner & Swasey Obs., 3, No.
2 (1989), avaiable via the CDS in directory .../III/156)' :-

TASS J062749.0+002949 = CGCS 1278

TASS J221942.8-003950 = CGCS 5627

[I note, for example, that a sizeable number of Takamizawa variables
listed as probable LPVs have been included as variables in the recently
released GCVS NameList 75 (IBVS 4870), and that a goodly proportion of
these turn out to be Carbon Stars listed in the CGCS]

[NB Not all, by any means, CGCS objects are identified with known
variables.  Most CGCS objects that are known variables are LPVs, but
some very small number are RCBs: eg SV Sge]

------------------------------------------------------------------------------------------------------

Note:

TASS J101131.7-001758 = RST 5345 = WDS10115-0018 = HD 88392
[9.9-10.2 V]                      [mag 10.1, 12.7, rho 2.1", theta
14deg]
                                       [Vj 10.2 (Tyc1), Vj 10.1 (Tyc2)]
                                       [A5/7 II (MHD Vol5 Houk+ 1999)]

I do not know what the resolution of the TASS instruments used on this
star is.  Two arcsecs' separation is small, but given nights of variable
seeing this [probably non-physical] double could be resolved some nights
and not others.  Two arcsecs' is a bit near the limit of resolution for
Tycho1, but Tycho2 can cope with this, so it looks like we have a V
10.1/10.2 star that appears a little brighter sometimes due to having a
12.7 mag stars light added.  [Unfortunately I can't find the combined
mag equation at the mo', just cos I need it!].  [For WDS2000 data see
www.usno.navy.mil, follow Astrometry Department link to WDS catalogue
links].

Note TASS log this star as an eclipser, but if so the quoted V 9.9
_maximum_ is _brighter_ than the other three independent assessments
[the WDS2000 value will be a visual estimate], whilst the quoted 10.2
_minimum_ fits the other estimates of the _usual_ magnitude.  I've not
heard of a class of eclipsing pairs with a late A type bright giant
primary, nor of many late A type bright giants for that matter, but this
doesn't mean such can't exist [probably folk with more astrophysical
nounce will know better].

On the face of it I feel this may be what the Tycho people call
'duplicity induced variability', which basically means that things are
apparently variable because a close pair are not properly resolved, and
resolved differently at every view.  I am quite willing and happy to be
proven wrong!
------------------------------------------------------------------------------------------------------

Other

TASS J074551.3+005538 = TmzV293

the combined datasets may clinch this one, dependant on passbands!


Cheers

John

John Greaves
UK

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